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Unformatted text preview: 1 Physics 1C Lecture 14A "The finest words in the world are only vain sounds if you cannot understand them."--Anatole France Sound Interference Example Two loudspeakers are 2.0m apart and are driven by the same oscillator. Both speakers emit 700Hz sound waves into a room where the speed of sound is 341m/s. A listener stands 5.0m in front of the speakers and 2.0m to one side of the center. Does the listener experience constructive interference, destructive interference, or neither at this location? Sound Interference Answer We need to calculate the path length difference, Δ r . So we should calculate the difference between r 2 and r 1. Speaker 1 5m 1m r 1 Speaker 2 5m 3m r 2 Sound Interference The path length difference at this location is a half-integer wavelength, so we should have destructive interference . <- Rounding to three places Comparing this to the path length difference gives: Answer Next, we should see how many multiples of the wavelength this path length difference is (integer, half- integer, or neither). So we should calculate the wavelength of this sound wave. Standing Waves in Strings For a string fixed at both ends, the longest standing wave we can achieve is: The frequency for this standing wave is known as the fundamental frequency or the first harmonic ....
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This note was uploaded on 02/11/2012 for the course PHYS 1C 1C taught by Professor Wethien during the Spring '11 term at UCSD.
- Spring '11